1. Field of the Invention
The present invention relates to the field of chemical disease control. More specifically, the invention relates to a method for controlling diseases of soybean by the application of glyphosate or mixtures of glyphosate and a fungicide to a glyphosate tolerant soybean MON89788.
2. Description of Related Art
The soybean, Glycine max (L.) Merril, is one of the major economic crops grown worldwide as a primary source of vegetable oil and protein (Sinclair and Backman, 1989). The growing demand for low cholesterol and high fiber diets has also increased soybean's importance as a health food.
Soybean yields in the United States are reduced each year by diseases. High yields per hectare are critical to a farmer's profit margin, especially during periods of low prices for soybean. The financial loss caused by soybean diseases is important to rural economies and to the economies of allied industries in urban areas. The effects of these losses are eventually felt throughout the soybean market worldwide. Estimates of loss due to disease in the United States and Ontario vary from year to year and by disease. From 1999 to 2002 soybean yield loss estimates were in the range of 8 million metric tons to 10 million metric tons in the United States and 90,000 to 166,000 metric tons in Ontario (Wrather et al, 2003).
Asian Soybean Rust (herein referred to as ASR) has been reported in the Eastern and Western Hemispheres. In the Eastern Hemisphere, ASR has been reported in Australia, China, India, Japan, Taiwan and Thailand. In the Western Hemisphere, ASR has been observed in Brazil, Colombia, Costa Rica, Puerto Rico among other places. ASR can be a devastating disease, causing yield losses of up to 70 to 80% as reported in some fields in Taiwan. Plants that are heavily infected have fewer pods and smaller seeds that are of poor quality (Frederick et al, 2002). ASR was first observed in the United States in Hawaii in 1994. ASR was later introduced into the continental United States in the fall of 2004, presumably as a consequence of tropical storm activity. Model predictions indicated that ASR had been widely dispersed throughout the southeastern United States, and subsequent field and laboratory observations confirmed this distribution.
N-phosphonomethylglycine, also known as glyphosate, is a well-known herbicide that has activity on a broad spectrum of plant species. Glyphosate is the active ingredient of Roundup® (Monsanto Co., St. Louis, Mo.), a safe herbicide having a desirably short half-life in the environment. When applied to a plant surface, glyphosate moves systemically through the plant. Glyphosate is phytotoxic due to its inhibition of the shikimic acid pathway, which provides a precursor for the synthesis of aromatic amino acids. Glyphosate inhibits the enzyme 5-enolpyruvyl-3-phosphoshikimate synthase (EPSPS) found in plants.
Glyphosate tolerance can be achieved by the expression of EPSPS variants that have lower affinity for glyphosate and therefore retain their catalytic activity in the presence of glyphosate (U.S. Pat. Nos. 5,633,435; 5,094,945; 4,535,060, and 6,040,497). Such genes are used for the production of transgenic crops that are tolerant to glyphosate, thereby allowing glyphosate to be used for effective weed control with minimal concern of crop damage. For example, glyphosate tolerance has been genetically engineered into corn (U.S. Pat. No. 5,554,798), wheat (U.S. Pat. No. 6,689,880), cotton (U.S. Pat. No. 6,740,488), soybean (WO 9200377) and canola (US 20040018518). The treatment of glyphosate tolerant crop plants with glyphosate has been shown to reduce disease incidence or severity (US 2005000654442 and US 2003000532758, both herein incorporated by reference).
This invention provides a method for treatment of a new glyphosate tolerant soybean event MON89788 (also referred to as MON19788 or GM A19788) with glyphosate to control various fungal diseases, especially Asian Soybean Rust disease.